/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.solr.handler;

import org.apache.solr.common.SolrException;
import org.apache.solr.common.params.SolrParams;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.common.util.SimpleOrderedMap;
import org.apache.solr.core.SolrCore;
import org.apache.solr.core.SolrInfoMBean;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.request.SolrRequestHandler;
import org.apache.solr.response.SolrQueryResponse;
import org.apache.solr.util.SolrPluginUtils;
import org.apache.lucene.queryParser.ParseException;

import java.net.URL;

/**
 *
 */
public abstract class RequestHandlerBase implements SolrRequestHandler,
		SolrInfoMBean {

	// statistics
	// TODO: should we bother synchronizing these, or is an off-by-one error
	// acceptable every million requests or so?
	volatile long numRequests;
	volatile long numErrors;
	volatile long numTimeouts;
	protected NamedList initArgs = null;
	protected SolrParams defaults;
	protected SolrParams appends;
	protected SolrParams invariants;
	volatile long totalTime = 0;
	long handlerStart = System.currentTimeMillis();
	protected boolean httpCaching = true;

	/**
	 * Initializes the {@link org.apache.solr.request.SolrRequestHandler} by
	 * creating three {@link org.apache.solr.common.params.SolrParams} named.
	 * <table border="1">
	 * <tr>
	 * <th>Name</th>
	 * <th>Description</th>
	 * </tr>
	 * <tr>
	 * <td>defaults</td>
	 * <td>Contains all of the named arguments contained within the list element
	 * named "defaults".</td>
	 * </tr>
	 * <tr>
	 * <td>appends</td>
	 * <td>Contains all of the named arguments contained within the list element
	 * named "appends".</td>
	 * </tr>
	 * <tr>
	 * <td>invariants</td>
	 * <td>Contains all of the named arguments contained within the list element
	 * named "invariants".</td>
	 * </tr>
	 * </table>
	 * 
	 * Example:
	 * 
	 * <pre>
	 * &lt;lst name="defaults"&gt;
	 * &lt;str name="echoParams"&gt;explicit&lt;/str&gt;
	 * &lt;str name="qf"&gt;text^0.5 features^1.0 name^1.2 sku^1.5 id^10.0&lt;/str&gt;
	 * &lt;str name="mm"&gt;2&lt;-1 5&lt;-2 6&lt;90%&lt;/str&gt;
	 * &lt;str name="bq"&gt;incubationdate_dt:[* TO NOW/DAY-1MONTH]^2.2&lt;/str&gt;
	 * &lt;/lst&gt;
	 * &lt;lst name="appends"&gt;
	 * &lt;str name="fq"&gt;inStock:true&lt;/str&gt;
	 * &lt;/lst&gt;
	 * 
	 * &lt;lst name="invariants"&gt;
	 * &lt;str name="facet.field"&gt;cat&lt;/str&gt;
	 * &lt;str name="facet.field"&gt;manu_exact&lt;/str&gt;
	 * &lt;str name="facet.query"&gt;price:[* TO 500]&lt;/str&gt;
	 * &lt;str name="facet.query"&gt;price:[500 TO *]&lt;/str&gt;
	 * &lt;/lst&gt;
	 * </pre>
	 * 
	 * 
	 * @param args
	 *            The {@link org.apache.solr.common.util.NamedList} to
	 *            initialize from
	 * 
	 * @see #handleRequest(org.apache.solr.request.SolrQueryRequest,
	 *      org.apache.solr.response.SolrQueryResponse)
	 * @see #handleRequestBody(org.apache.solr.request.SolrQueryRequest,
	 *      org.apache.solr.response.SolrQueryResponse)
	 * @see org.apache.solr.util.SolrPluginUtils#setDefaults(org.apache.solr.request.SolrQueryRequest,
	 *      org.apache.solr.common.params.SolrParams,
	 *      org.apache.solr.common.params.SolrParams,
	 *      org.apache.solr.common.params.SolrParams)
	 * @see SolrParams#toSolrParams(org.apache.solr.common.util.NamedList)
	 * 
	 *      See also the example solrconfig.xml located in the Solr codebase
	 *      (example/solr/conf).
	 */
	public void init(NamedList args) {
		initArgs = args;

		// Copied from StandardRequestHandler
		if (args != null) {
			Object o = args.get("defaults");
			if (o != null && o instanceof NamedList) {
				defaults = SolrParams.toSolrParams((NamedList) o);
			}
			o = args.get("appends");
			if (o != null && o instanceof NamedList) {
				appends = SolrParams.toSolrParams((NamedList) o);
			}
			o = args.get("invariants");
			if (o != null && o instanceof NamedList) {
				invariants = SolrParams.toSolrParams((NamedList) o);
			}
		}

		if (initArgs != null) {
			Object caching = initArgs.get("httpCaching");
			httpCaching = caching != null ? Boolean.parseBoolean(caching
					.toString()) : true;
		}
	}

	public NamedList getInitArgs() {
		return initArgs;
	}

	public abstract void handleRequestBody(SolrQueryRequest req,
			SolrQueryResponse rsp) throws Exception;

	public void handleRequest(SolrQueryRequest req, SolrQueryResponse rsp) {
		numRequests++;
		try {
			SolrPluginUtils.setDefaults(req, defaults, appends, invariants);
			rsp.setHttpCaching(httpCaching);
			handleRequestBody(req, rsp);
			// count timeouts
			NamedList header = rsp.getResponseHeader();
			if (header != null) {
				Object partialResults = header.get("partialResults");
				boolean timedOut = partialResults == null ? false
						: (Boolean) partialResults;
				if (timedOut) {
					numTimeouts++;
					rsp.setHttpCaching(false);
				}
			}
		} catch (Exception e) {
			SolrException.log(SolrCore.log, e);
			if (e instanceof ParseException) {
				e = new SolrException(SolrException.ErrorCode.BAD_REQUEST, e);
			}
			rsp.setException(e);
			numErrors++;
		}
		totalTime += rsp.getEndTime() - req.getStartTime();
	}

	// ////////////////////// SolrInfoMBeans methods //////////////////////

	public String getName() {
		return this.getClass().getName();
	}

	public abstract String getDescription();

	public abstract String getSourceId();

	public abstract String getSource();

	public abstract String getVersion();

	public Category getCategory() {
		return Category.QUERYHANDLER;
	}

	public URL[] getDocs() {
		return null; // this can be overridden, but not required
	}

	public NamedList getStatistics() {
		NamedList lst = new SimpleOrderedMap();
		lst.add("handlerStart", handlerStart);
		lst.add("requests", numRequests);
		lst.add("errors", numErrors);
		lst.add("timeouts", numTimeouts);
		lst.add("totalTime", totalTime);
		lst.add("avgTimePerRequest", (float) totalTime
				/ (float) this.numRequests);
		lst.add("avgRequestsPerSecond", (float) numRequests * 1000
				/ (float) (System.currentTimeMillis() - handlerStart));
		return lst;
	}

}
